I've always wanted to write history, and it was only the accident of going to work for a book publisher in 1958 (and the need to earn a regular paycheck) that slowed me down. Even then, I went through a long, self-imposed, part-time apprenticeship: I began small, and apparently in the wrong direction, with magazine articles, then moved on to write "self-help" books that grew out of them, like Power!; from there into fiction (Queenie), then memoirs (Charmed Lives), before, quite late in life, I finally began to write what I probably should have started out writing 40 years ago, for my role models were, and still remain, Barbara Tuchman, Garrett Mattingly, and Sir Arthur Bryant.

From the age of 12 I've been an avid and omnivorous (if slightly undiscriminating) reader of history and biographies, with a marked—in some people's view alarming—interest in military history and military figures, a taste which was not, strangely enough, at all diminished by my service in the Royal Air Force. Even as a boy in England I devoured books on the U.S. Civil War—Bruce Catton's books had an enormous effect on me when I was about 15, opening up to me a subject I knew nothing about—so when in 2003 James Atlas, who was then publishing a series of short biographies called Eminent Lives, asked me whether I would like to do one, and, if so, of whom, I instantly replied, "Grant!"

I had always admired Ulysses S. Grant, who seemed to live on in history in the shadow of Robert E. Lee, the man he defeated, and I looked forward to learning more about that curiously shy yet amazingly determined figure—since for me, the writing of history and biography is above all an adventure, a process of discovery, of learning everything I can about a person or a period that interests me. The novelist wants to know how things will turn out; the historian already knows how things turned out, but wants to know why they turned out the way they did. Thus I wrote about the Battle of Britain (With Wings Like Eagles) because I wanted to know how we managed to win it despite years of reluctance to rearm and the appeasement of Hitler.

I do not start with a full knowledge of the facts; the whole attraction of writing history is to educate myself: it is an exploration into the unknown, "a journey without maps," to borrow Graham Greene's phrase. Curiosity is the best motive for writing: curiosity about the world at large, or about oneself. Thus, I thought that Dwight D. Eisenhower, like Grant, was a far better general than he is given credit for (and a better president, too), and wrote Ike to see if I was right about him.

T.E. Lawrence, I always wanted to do. My uncle, the film producer Sir Alexander Korda, gave me a copy of Seven Pillars of Wisdom for my 16th birthday and left me (among other things) his copy of The Letters of T.E. Lawrence. Alex had known and liked Lawrence, and indeed bought the movie rights to Revolt in the Desert, with Leslie Howard in mind to play Lawrence, but agreed over a rare but cordial lunch with the author (who was then serving in the R.A.F. as AC1 Shaw) not to make a film while Lawrence was still alive. (Alex kept his promise, and eventually sold the rights, the film script that Winston Churchill had helped write, and my father Vincent Korda's production designs to Sam Spiegel after WWII, enabling David Lean to turn Lawrence's story into one of the most successful films of all time.) I wanted to know how Lawrence stepped almost overnight from obscurity into the full glare of worldwide celebrity in his own lifetime, how he became perhaps the only hero of WWI whose name people still remember today in the English-speaking world, and, above all, how a young, slightly built man in his 20s turned himself into a military genius and invented the methods of insurgency that we are still trying to defeat in Iraq and Afghanistan.

Lawrence is, of course, the Moby-Dick of English biographical subjects, mysterious, attractive, "a dangerous man," as Bernard Shaw called him, his motives and his actions constantly mystifying or surprising those who write about him, and still leaving in his wake, 75 years after his death, controversy, puzzles, missing pieces, an aura of legend that often obscures fact. Yet the facts are there—nobody ever wrote more or longer (or more honest) letters, or a better account of his own war experience—and the challenge is not from any lack of material but to take the vast mass of material and sift through it for a coherent story and a believable portrait.

I can't imagine anything else I would rather have written about, or any journey of discovery I would have more enjoyed.

Michael Korda was the editor-in-chief of Simon & Schuster. His new book is Hero: The Life and Legend of Lawrence of Arabia.